I originally posted this on the Episode forum but got no response. I hope someone here can help:
I am delivering some 16x9 Flash videos to a client in 2 sizes: 640x360 and 480x270, using Episode. The problem is this: The 640x360 movies look terrific; very sharp. The 480x270 movies all show jagged edges, particularly on text. It looks as though a comb has been dragged across the image vertically. I think the image has been stretched horizontally during the encoding. But the aspect ratios are all perfect 16x9 so I don't understand how that would happen.
I have tried all kinds of solutions including increasing data rates, using three different methods of maintaining aspect ratio, etc.,but I cannot get good looking Flash files at 480x270.
I'd appreciate any suggestions. (Octocore, self-contained full-res source files from Final Cut Pro, using OS 10.5.8 and Episode v.5.3.1.)
Try doing the smaller one at 480x272. Adobe recommends that pixel sizes be multiples of whole numbers, with 16 being the multiple that produces the best encoding results.
I believe this has to do with how compression schemes compress the image. I've read that H264 compresses in blocks of 16x16 pixels, so that would explain why you'll get better results using multiples of 16.
I don't know for sure that this will correct your problem, but it's the only reason I can think of that your smaller version doens't look as good.